This invention relates to radio transceivers and, in particular, to radio transceivers having variable or boosted power supplies.
Radio communication transceivers designed for mobile vehicle applications are normally operated directly from the vehicle power supply which power supply consists of a conventional storage battery with an engine-driven charging system. Because most vehicles have a standardized 12 volt electrical system, most mobile radio communication equipment is designed to operate on voltages ranging from 12 volts to 14 volts.
Radio receiving circuits are easily designed to operate efficiently at relatively low voltages. However, transmitter circuits and, more particularly, radio frequency power amplifier circuits operate more efficiently at higher voltages than are typically available from a vehicle electrical system. For example, transistorized radio frequency power amplifier stages are far less costly if they can be operated from a 24 volt direct current power supply rather than a 12 direct current power supply for a given output power. Since the high power, radio frequency amplifier transistors designed for VHF and UHF mobile transceivers are by far the most expensive components in such systems, it is most desirable to operate these radio frequency power amplifier stages at higher voltages. An added benefit of operating at higher voltages, for given output powers, is that the thermal protection circuitry designed to protect the transistors from load mismatches and thermal runaway are less critical. Furthermore, most transceivers used for mobile communications, and especially the low cost citizens band transceivers, are particularly sensitive to power supply voltage variations. For example, a reduction of 2 to 3 volts in supplied power will reduce the radio frequency output power up to one half. Voltage variations of this magnitude are typical in vehicular battery/alternator electrical power sources.
One solution to the above problem is to use a conventional DC to DC solid state inverter to increase the available supply voltage to a transceiver. However, reliable inverters are expensive and exhibit switching noise which, unless well filtered, may interfere with radio reception.
The subject invention overcomes many of the problems of the prior systems by powering the transmitter amplifying stages of the transceiver at a higher voltage than the balance of the circuitry. The present invention can be incorporated into existing transceivers since a nominal increase in operating voltage, such as 25% increase, may be safely handled by most solid state transceivers. In accordance with the subject invention, a secondary power supply is charged from the primary power supply during the receive mode and is automatically switched into series with the primary power supply during the transmit mode.
Accordingly, the subject invention includes a power booster assembly for a transceiver having connection means for connection to a primary power supply and including a secondary power supply and circuit means adapted for electrical connection to the connection means for switching the secondary power supply into and out of series with the primary power supply.